1. Field of the Invention
The present invention relates to an improvement to a regenerative pump used as a vehicle fuel pump, etc., and particularly to a pump of wich pump efficiency is improved by increasing a delivery pressure without decreasing a flow rate compared to a conventional pump.
2. Description of the Prior Art
Non-contact type pumps and non-positive displacement pumps are known as examples of regenerative pumps. The regenerative pump is provided with an impeller, and the impeller comprises a flat disc-shaped base plate, a plurality of concave channels formed along peripheral edges on both sides of the base plate, and blades positioned between the concave channels so as to extend in a radial direction of the base plate. The impeller is housed in a pump chamber formed in a housing. The impeller is supported in the pump chamber by a shaft passing through the center of the base plate and is rotated within the plane vertical to the shaft. Liquid flowing through an inlet port formed in the housing is delivered at high pressure from an outlet port formed in the housing.
For a generally known conventional regenerative pump, as shown assigned with reference symbol P01 in FIGS. 16 and 17, an impeller 3 which is housed and rotated in a pump chamber of a housing 1, is formed in a flat disc-shaped base plate. Along the peripheral edges on both sides of the base plate, a plurality of concave channels 5 are formed at even intervals in the peripheral direction of the base plate and further formed in such a way as to be gradually deeper from the radially innermost ends to the radially outer most ends thereof. Blades 4 having a constant thickness in the peripheral direction are formed so as to extend in the radial direction of the base plate. The pump chamber accommodating the impeller 3 is provided with flat inner side walls 6 opposite to flat surfaces of the base plate, cylindrical inner peripheral wall 7 opposite to the peripheral tip ends of the blades 4 formed along the outer circumferential edge of the base plate, and arcing grooved wall surfaces 8 opposite to the side surfaces of the blades 4 for connecting the flat inner side walls 6 to the cylindrical inner peripheral wall 7 as well as forming a fluid passage 2 connecting the inlet port to the outlet port (neither of which is shown), both being formed in the housing 1.
In this conventional type of regenerative pump P01, liquid flow LM arising from friction between the blades 4 and liquid is generated in the fluid passage 2 in the direction of the rotation of the impeller 3 designated by allow F, as a result of the rotation of the impeller 3. Further, liquid flow LB is generated in the radial direction of the impeller 3 along surfaces 9 of the blades 4 which forwardly face in the direction F of the rotation of the impeller 3. This flow LB merges with the flow LM within the fluid passage 2. As a result of this, a decrease in the flow velocity of the liquid flow LM that are introduced from the inlet port and flow through the fluid passage 2 results in the conversion of velocity energy into pressure energy, whereby the liquid are delivered from the discharging opening at a high pressure.
Japanese Unexamined Patent Application Gazette No. Hei 2-45690 published in 1990 discloses an improved regenerative pump shown in FIGS. 18 and 19. For this pump P02, as is evident from FIG. 18, the thickness in the peripheral direction of each blade 4 of the impeller 3 gradually increases as the radius of the impeller 3 decreases. The edge of each concave channel 5 closer to the center of the rotation of the impeller 3 assumes a contour which joins two arc surfaces 4a and 4b.
This pump P02 is the same as the pump P01 in that the center of the thickness in the peripheral direction of each blade 4 is positioned in one radial line passing through the center of the rotation of the impeller 3. However, compared to the pump P01, the pump P02 can produce an increased pump delivery pressure because the liquid flow LB developed in the concave channels 5 flows smoothly by virtue of the existence of the arc surfaces 4a and 4b. However, if the radial length of the blades 4 is the same as the length of the blades 4 of the pump P01, the volume of the concave grooves 5 will be reduced, which causes a flow rate of the pump to be reduced, Hence, no improved pump efficiency is attained.